1. Field of the Invention
The present invention relates to a display device usable for optical elements such as a light control glass, a light control element, a display element, and a display method using the display device.
2. Description of the Related Art
Along with the advancement of a highly information-oriented society, there has been an increased need for electronic paper systems, color display systems, and large surface area display systems.
Particularly, there is great need for next-generation electronic paper display systems. However, presently no promising technology has been established get for satisfying the need. Possible known method include a liquid crystal method, an electrophoresis method, and a twist ball method, and the like.
The liquid crystal method utilizes a polarization plate. Therefore, light utilization factor is low, resulting in problems in that the reflectivity is decreased, making it difficult to display images with high quality.
As a display device employing the electrophoresis method, for example, a display device having a structure formed by sealing a plurality of electrically charged and colored electrophoresis particles and an insulating liquid in which coloring material with different coloration from those of the electrophoresis particles is dissolved between substrates is disclosed in Japanese Patent Application Laid-Open (JP-A) No 11-202804. In this device, images are displayed by transferring electrophoresis particles in accordance with the voltage applied between the substrates and showing contrast between the electrophoresis particles and the insulating liquid. However, the device has problems in that replacement of a plurality of colored electrophoresis particles is sometimes incomplete so that light leakage among particles takes place, and the contrast and the reflectivity deteriorate owing to the electrode structure.
Further, as a display device employing the twist ball method, a rotating twist ball or Gyricon display device has been known. This device comprises dichroic balls each having a first color (e.g. white color) in approximately a half or 50% of the sphere and a second different color in the other half of the sphere (e.g. black color). These dichroic balls are suspended in liquid hollow parts in an elastomer or polymer sheet sandwiched between glass or plastic films. For example, U.S. Pat. No. 4,126,854 describes that in a device having such a structure, the dichroic balls rotate along with their electric anisotropy or bipolar to form images. However, this display device has low optical density. Further, due to the difficulty in controlling in the rotation and obtaining a precise dichroic property, there is a problem in that neither high reflectivity nor high contrast can be obtained.
In addition, as a display device other than the aforementioned methods, JP-A No. 56-88173 discloses a device having a mechanism of utilizing an electrophoresis of a liquid material to a porous body and scattering outside light by controlling the content of the liquid in the surface of the porous body. However, the display device with this mechanism has a display structure in which one surface part of the porous body is exposed. Therefore, it is poor in portability and cannot be applied to electronic paper.
Further, JP-A Nos. 10-35095 and 10-44592 disclose recording methods and recording media for forming images by moving ink materials by outside forcible forces such as electroosmosis to visible regions in the surfaces of the porous layers and eliminating the images by moving the ink materials by outside forcible forces to invisible regions. However, these recording methods and recording devices have a problem cannot be done in that the images to be displayed are predetermined and re-writing.